[time-nuts] WWVB BPSK Receiver Project?

J. Forster jfor at quikus.com
Thu Mar 15 04:14:41 UTC 2012


> On 3/14/12 8:07 PM, J. Forster wrote:
>>> John
>>> Like your thought. I seem to remember costas loops work like that to
>>> recover the carrier.
>>
>> Paul,
>>
>> It recovers a bipolar signal to steer the local VCO as well as the
>> data..
>> It also needs a quadratue hybrid at the VCO frequency (although it might
>> be fairly easy to make a quadrature oscillator vat 60 kHz.)
>
> One easy scheme is to make your VCO run at a multiple and divide down to
> generate the two quadrature square waves.

Doesn't look like that works with the HP 117A. I don't know about other
receivers.

>>> Had seen it in amsat many years ago. So perhaps an approach is to limit
>>> if possible the incoming signal.
>>
>> I'm not sure if it works properly with clipped (digital) dignals, off
>> hand.
>
> Yes it will.

Not w/o a quadrature drive to the mixer/multiplier. A square wave,
multiplied by itself, has the same output as input.

>>> Though further simple dumb thought. A NE602 or SA602 or also teh 612
>>> series. All the same mixer circuit (Or multiplier)will double the
>>> incoming
>>> frequency if you delay the incoming by 90 degrees I think.
>>
>> Sine and Cosine are orthogonal. You need to do (Sine)*(Sine)
>>
>> sin^2 (wt) = 1/2(1 - cos (2wt)
>>
>
> This is like the classic squaring technique to receive PN coded signals
> without knowing the code.  (it's used in some "codeless" GPS receivers..
> you can retrieve frequency and phase)

A Costas Loop recovers the bit stream and the carrier frequency (from the
local VCO) from a BPSK. It is self syncronizing.

I'm beginning to think that, for the HP 117A at least, a fix could be
built on a small daughter board.

Also, I think that NIST should do the engineering and maybe run the boards
too.

-John

===============






More information about the Time-nuts_lists.febo.com mailing list